Here are 10 windmills in Kent which are regularly open to the public, 7 of them maintained by Kent County Council. A leaflet giving opening times and contact details for these mills (and others) can be found
HERE

Shire Books have four books at reasonable prices by Martin Watts, a miller and millwright; you can find out more about them HERE

Second-hand but worth looking for:Windmills in England and A Source Book of Windmills and Watermills by Rex Wailes

Windmill World has an extensive list of Windmill books, both in and out of print.

MORE Links to Related Sites

Kent Mills - gives more information on contact details and opening times

The Mills Archive has nearly 400 items relating to the Union Mill at Cranbrook; an index of their holdings is HERE
There is a lot more detailed historical information about mills in Kent to be found in articles onder the heading Kent Millers' Tales.

Mills Section of the Society for the Protection of Ancient Buildings (SPAB)

Windmills on Wikipedia - history, evolution, types of mill, and machinery - with lots more links
Wikipedia also lists Windmills in Kent and includes some which have been converted to houses and some where only part of the mill building has survived.